Debra and Dale Krein sued in 2012 after enduring years of what they deemed incessant barking by several Tibetan Mastiff dogs owned by their neighbours, Karen Szewc and John Updegraff, court documents showed.

A jury awarded the Kreins $238,000 (NZ$331,000), and the presiding judge ordered all the dogs on the property to undergo "total devocalisation" surgery.

The dogs' owners appealed that decision and the Oregon Court of Appeals on Wednesday upheld the judgement and surgery order.

The appellate court wrote in its 14-page ruling that the lower court had the authority to impose the surgery because of the "persistent failure" of the couple to remedy the barking.

Devocalisation surgery entails cutting an animal's vocal cords "to decrease the volume, pitch and intensity of the dog's bark," according to literature provided by the American Veterinary Medical Association.

The AVMA says the operation should be used "as a final alternative to euthanasia" after all behaviour modification efforts have failed and the animal's owner is told of the risks.

Scott Beckstead, senior director for the Oregon chapter of the Humane Society of the United States, said there were other remedies to deal with nuisance barking, including sprays.

"This ruling came as a complete shock to us," Mr Beckstead said.

The American Society for the Prevention of Cruelty to Animals said it also opposed the technique.

"The ASPCA does not support the use of surgical procedures that attempt to circumvent the behavioural issue while exposing pets to unnecessary discomfort and risk," it said in a statement.

Neither Updegraff or Szewc could be reached for comment, but Szewc told the Oregonian newspaper the dogs protected the couple's flock of sheep.

"We do not have the dogs to harass the neighbours," the newspaper quoted her as saying.

The Kreins' lawyer, Mike Franell, said the court reached the right decision.

"My clients have suffered well over 10 years of incessant barking," Mr Franell said.